1. Field of the Invention
The present invention relates to a process for producing a phenylacetone or its derivative.
2. Description of the Prior Art
Phenylacetone and its derivatives ("phenylacetones" hereinbelow) are useful as intermediates for various agricultural chemicals and pharmaceutical preparations. For example, 4-hydroxy-3-methoxyphenylacetone (HMPA), 3,4-dimethoxyphenylacetone (DMPA), and 3,4-methylenedioxyphenylacetone are utilized as intermediates for producing L-alpha-methyldopa, which is used as antihypertensive. Thus, the phenylacetones are practically useful compounds. However, industrially satisfactory processes for producing phenylacetones have not yet been developed.
For instance, British Patent Specification No. 1119612 discloses a process for producing DMPA by reacting 1-(3,4-dimethoxyphenyl)propylene with peroxides such as peracetic acid, followed by treating the resultant diol type products with acidic substances such as zinc chloride. However, this process is not entirely satisfactory in industrial use because the yield of the treatment step with an acidic substance is low and that the special caution should be taken in the handling of the peroxides because of their explosive properties.
Furthermore, the Journal of the American Chemical Society (J.A.C.S.) 77, 700 (1955) discloses a process for producing DMPA by reacting 3,4-dimethoxyphenyl acetonitrile with sodium ethoxide in a solvent such as ethyl acetate to form the acetylated product, followed by hydrolysis. However, this process includes problems that water should be completely removed from the reaction system, which sodium ethoxide is used, in order to prevent hydrolysis of the sodium ethoxide, that the yield of the desired product in the hydrolysis step is low, and that the large number of steps in the entire process is required taking into account the steps necessary to prepare the starting 3,4-dimethoxyphenyl acetonitrile from a readily available chemical raw material.